1. Technical Field
The present invention relates to a light emitting device mainly having an excitation light source, a wavelength conversion member, and a light guide.
2. Background Art
Conventionally, endoscope devices for in vivo observations and for performing treatment during observations, and fiber scopes for observing in extremely narrow or dark spaces have been widely used.
Endoscopes and fiber scopes are constructed with extremely minute light guides and are able to illuminate spaces or the like such as inside body cavities like the stomach or other gaps or the like because the fibers transfer light which has been radiated from a light source.
In order to efficiently illuminate using minute fibers, the light source is required high brightness. Furthermore, when observing and in some cases diagnosing an affected area of an organ or within cavities, accurate reproduction of color information is important. Thus, the light source for endoscopes and fiber scopes require light which is close to natural light.
Further, in order to shorten the time a patient has to wait after the light source of an endoscope is turned on, it is necessary to use a light source of extremely high reliability so that the light will instantly come on and stabilize, and will not go out during use.
Examples of light sources that have been used in such applications include xenon lamps and metal halide lamps.
However, problems encountered with a xenon lamp or a metal halide lamp are that a vivid color cannot be achieved, it takes a long time for the color of the emitted light to stabilize, and the light cannot be instantly turned back on, among others.
Consequently, it has been proposed that a light emitting diode element (LED), laser diode element (LD), or other such semiconductor light emitting element be used instead of a xenon lamp or the like as the light source (see Japanese Laid-Open Patent Application 2002-95634, for example).
As shown in FIG. 17, a conventional endoscope device 100 is made up primarily of an image processing signal component 101 and an endoscope insertion component 102, and a white light source 111 equipped with a red semiconductor laser 111a, a green semiconductor laser 111b, and a blue semiconductor laser 111c is mounted in an illumination unit 110 in the image processing signal component 101. The semiconductor lasers 111a to 111c emit light in multi-vertical mode having a spectrum distribution with little interference and a plurality of wavelengths λ, and white light is obtained by mixing light of the three primary colors. The light emitted from this illumination unit 110 is guided by a light guide 103 to the endoscope insertion component 102.
A semiconductor light emitting element is small in size, has good electrical power efficiency, and emits light of vivid color. Also, because this element is formed from a semiconductor, there is no worry about burnt-out bulbs or the like. Furthermore, the initial drive characteristics are excellent, and such an element stands up well to vibration and to being repeatedly switched on and off. In particular, a semiconductor laser has far higher emission intensity than a light emitting diode, and therefore can be used as a light source with high luminance.